Concentric rotary fluid machines may be operated as a pump or alternately as a motor/drive. When operated as a pump, external torque is provided to a rotating part of the machine which in turn provides positive displacement for fluid thereby providing a pumping action. When used as a drive, fluid is pumped through the machine causing one body or component to rotate relative to another thereby providing torque which may be used to drive a tool, mechanism, or system. Throughout this specification the term “fluid” is to be given its ordinary meaning and includes a liquid, gas, or other substance or composition that is able to flow and/or otherwise yields to pressure. Non limiting examples of a fluid include, water, oil, liquid air, liquid nitrogen and drilling muds.
Examples of a type of concentric rotary fluid machine to which the present disclosure relates are disclosed in U.S. Pat. Nos. 6,280,169; 6,468,061; 6,939,177; and, 6,976,832 (all of which are hereby incorporated by reference in their entirety). This type of machine has a rotor and a stator which are concentrically arranged one inside the other to define a working fluid space there between. One of the rotor and stator is provided with one or more lobes and the other is provided with or supports one or more gates or vanes. Whichever one of the rotor and stator supports the gate is sometimes referred to as the “supporting body” of the machine. The other is sometimes referred to as the “non-supporting body” of the machine. When the machine is used for example as a drive or a motor, a fluid is pumped through the machine, passes into the working fluid space through various inlets, and exits the working space through one or more outlets. A movable gate or vane is always maintained between the inlets and outlets to effectively divide the working chamber into alternating high pressure and low pressure chambers. The pressure of fluid entering through the inlets acts equally on all components within the working chamber and consequently has the effect of causing the rotor to rotate. This in turn progressively moves the gates or vanes relative to the outlets so that eventually the high pressure fluid is itself displaced to a rotationally adjacent outlet.
The efficiency of operation of such a machine, its ease of manufacture and susceptibility to failure is dependent on numerous factors including but not limited to: the design and configuration of the gates/vanes that extend into the working fluid space; the configuration of the recesses or slots into which the gates or vanes retract into when contacted by a passing lobe; the relative configuration and sealing efficiency of a lobe against the recess/slot; and friction between relatively moving components.
In a machine having one or more swinging gates, during relative rotation of the rotor and stator, when a gate is fully extended contact between a lobe and a gate initially occurs at a location adjacent a swing axis of the gate. As rotation continues, eventually the lobe contacts a distant free end of the gate. In order to create an effective seal the lobe and the gate must be formed with substantially matching curved surfaces to prevent high pressure from leaking between the gate and the lobe to an adjacent low pressure side when the lobe and the gate are in mutually radial adjacent relationship. This presents challenges in manufacture to produce components to high tolerance specifications not only to minimise this pressure leakage but also to facilitate the overall fit of the components that make up the machine.